The purpose of this study is to create conditionally immortalized human urothelial cell lines that retain key differentiated features of the highly specialized urothelium. This model will eliminate the need for unpredictable, short-lived primary cultures obtained from human subjects, and provide a consistent and self-renewing resource for the objective evaluation of current and future treatments for interstitial cystitis. When the cell line is established, we will determine how intravesical treatments (which are thought to restore the protective glycosaminoglycan layer) affect urothelial function. This will be the first objective evaluation of these empiric treatments. We will also evaluate potential diagnostic urinary markers for IC. Immortalized cell culture lines. We will first establish primary cultures from human cystoscopic biopsy specimens. These cell lines will be immortalized with a retroviral construct containing a thermosensitive version of the SV40 large-T antigen. This will allow the urothelial cells to proliferate indefinitely, providing a reliable supply of cells. Urothelial differentiation can be induced by thermoshift to nonpermissive culture conditions. A model for the urothelium in IC. Disruption of the cultured urothelium with protamine sulfate creates a state similar to interstitial cystitis. Evaluation of intravesical therapies. Heparin and hyaluronic acid are currently thought to restore the glyosaminoglycan layer that protects the urothelium, but this has never been proven. The urothelium will be disrupted, and the urothelial function will be assessed. Heparin or hyaluronic acid will be instilled into the culture media (similar to the way they are applied in the bladder), and the same parameters will be measured after treatment. Evaluation of urinary markers. The cellular effects of antiproliferative factor and glycoprotein 51 will also be evaluated. In summary, treatments for interstitial cystitis have been difficult to evaluate because of the lack of a reliable cell culture model, and many therapies are used empirically. An immortalized cell culture line will enable us to directly evaluate current therapies, and facilitate the development of novel treatments for interstitial cystitis.